The U.S. military cleared the F-35 Joint Strike Fighter to return to flight on Thursday, ending a week-long cautionary grounding that was ordered after an engine inspection revealed a cracked turbine blade on an F-35A test aircraft at Edwards Air Force Base, Calif. The February 21 grounding affected all three variants of the fighter.

Pratt & Whitney, manufacturer of the aircraft’s F135 engine, said a 0.6-inch crack was found on a third-stage low-pressure turbine blade during a routine engine inspection. The company conducted “comprehensive” tests on the turbine module at its engine facility in Middletown, Conn.

“The engine in question is part of the F-35 test aircraft fleet and had been operated for extended time in the high-temperature environment in its mission to expand the F-35 flight envelope,” Pratt & Whitney said in a statement provided to AIN. “Prolonged exposure to high levels of heat and other operational stressors on this specific engine were determined to be the cause of the crack.”

The company said no cracks were found during inspections of the remaining F135 inventory. F-35s are currently assigned to Edwards AFB; Patuxent River Naval Air Station, Md.; Eglin AFB, Fla.; and Marine Corps Air Station Yuma, Ariz.